“Wireless devices” include in general any device capable of connecting wirelessly to a network, and includes in particular mobile devices including mobile or cell phones (including so-called “smart phones”), personal digital assistants, pagers, tablet and laptop computers, content-consumption or generation devices (for music and/or video for example), data cards, USB dongles, etc., as well as fixed or more static devices, such as personal computers, game consoles and other generally static entertainment devices, various other domestic and non-domestic machines and devices, etc. The term “user equipment” is often used to refer to wireless devices in general, and particularly mobile wireless devices.
A multi-SIM (subscriber identity module) wireless device, including particularly mobile devices such as mobile phones (including so-called “smart phones”), personal digital assistants, tablet and laptop computers, etc., can hold two or more SIM cards. Currently, such devices can typically hold two SIM cards, though phones that can hold three SIM cards are now available and it is likely that phones and other wireless devices that can hold more SIM cards will become available. For simplicity and brevity, reference will often be made in this specification to a dual-SIM device, which can operate with two networks and/or tariff arrangements, etc., but it will be understood that much of what is described herein can be applied to a multi SIM wireless device having in principle any number of SIMs for operating with a corresponding number of networks and/or tariff arrangements, etc. It is mentioned here that there are proposals to replace SIM (subscriber identity module) cards with SIM functionality provided by software in the device. Reference will be made in this specification generally to “SIM” to mean that part of a device that provides for the subscriber identity module functionality whether provided by a physical card, software elsewhere in the device, or any other suitable arrangement.
Dual-SIM operation allows the use of two services without the need to carry two devices at the same time. For example, the same handset can be used for business and private use with separate numbers and bills. As another example, the same handset can be used for travel, with one SIM being for use in the home country and the other SIM being for the country visited. As another example, both SIMs may be used with the same network operator, for example to achieve a higher total bandwidth for data connections. As yet another example, the device may contain both cellular and non-cellular radios which are used for voice and data communication respectively using the different SIMs. In any event, using multiple SIMs allows the user to take advantage of different pricing plans for calls and text messages to certain destinations as well as mobile data usage, and/or to keep personal and business use separate for example, and/or to achieve higher bandwidth, and/or to obtain coverage across different networks using a single handset. With this multiple SIM functionality, the SIMs can in general be from any network operator. The embodiments described herein are particularly concerned with mobile wireless devices that have two (or more) SIMs that share a radio system. These will typically be referred to herein as “dual-SIM, single radio devices” though it will be understood that this is to be taken to include any device that has plural SIMs where at least two of the SIMs share a radio system. The term “radio system” or just “radio” is typically used in this specification to refer to one or more of the radio front end, antenna(s), and relevant processing circuitry and software required for transmission/reception in a wireless device, unless the context requires otherwise.
Dual-SIM, single radio devices can provide a functionality referred to as “dual-SIM dual-standby”, which means that in standby (or idle mode) either SIM is able to originate or terminate a connection (for example a call or data connection for email, texts, etc.). In particular, when both SIMs are in idle mode, pages can be received because these occur infrequently so it is possible for the two SIMs to use the radio on a time-shared basis. However, as soon as one SIM enters an active connected mode, it is given control of the radio and the other SIM is not able to transmit or receive any data (at least in the case of some radio access technologies). As a particular example, this means that the other SIM cannot receive indications of incoming calls, which is often not acceptable to users. This is particularly so if for example the one SIM is being used by an application, such as an email client, that has an ongoing packet data connection which could be ongoing for many hours. In such a case, the user may not even be aware of the ongoing packet data connection and thus not even know that the wireless device is for example unable to receive or even be notified of an incoming voice call. It is likely that a voice call on the other SIM would be more important to the user than the ongoing packet data connection for receiving email.